Chart library examples — monadic vs pure API

01_ExampleMonadic.hs

plotSpectrum1 lattice n m = toFile def file $ do
    layout_title .= "Spectrum of '" ++ name ++ "'"
    layout_x_axis . laxis_title .= "momentum k (" ++ show m ++ " points)"
    layout_y_axis . laxis_title .= "energy E"
    setColors $ colorGradient blue (length rows)
    forM_ rows $ \row -> plot (line "band" [row])
    
    where
    ...

colorGradient color n =
    [opaque $ blend (fromIntegral k/fromIntegral n) black color | k <- [1..n]]

02_ExamplePure.hs

plotSpectrum' n m = renderableToFile def file $ toRenderable chart
    where    
    chart = tval energyBands

    energyBands
        = layout_title .~ "Spectrum - '"  ++ name ++ "'"
        $ layout_x_axis . laxis_title .~ "momentum k (" ++ show m ++ " points)"
        $ layout_y_axis . laxis_title .~ "energy E (" ++ show n ++ " bands)"
        $ layout_plots .~ map (toPlot . plotBand) (zip bands colors)
        $ def
    colors = colorGradient blue (length bands)

    plotBand (band,c)
        = plot_lines_values .~ [map (\(x,y,z) -> (x,y)) band]
        $ plot_lines_style . line_color .~ c
        $ def
    
    ...
colorGradient color n =
    [opaque $ blend (fromIntegral k/fromIntegral n) black color | k <- [1..n]]

03_ExampleMatlab.m

% test data (to keep example self-contained)
ks = 0:0.1:pi; m = length(ks);
bands = transpose([sin(ks); sin(2*ks); sin(3*ks)]); % m * 3 matrix


% plotting functionality
gradient = transpose( [ zeros(1,m); zeros(1,m); 1 - ks / pi ])
set(0, 'DefaultAxesColorOrder', gradient)

plot(bands)
xlabel(sprintf('momentum k (%d points)',m))
ylabel('energy E')
title('Spectrum of Hamiltonian')